[RFC PATCH V4 0/2] Btrfs: get/set mounted filesystem label support

[RFC PATCH V4 0/2] Btrfs: get/set mounted filesystem label support

[Jeff Liu]

Hello,

This is an improved tiny patch set to add get/set the label upon a mounted
file system via ioctl(2).

I'd like to add the Signed-off-by with Anand for the credit since He has posted a
similar patch set a few month ago.


Changes of V4->V3:
- Add a new ioctl to fetch the label of a mounted file system.
- Replace "struct btrfs_ioctl_fs_label_args" with "char label[BTRFS_LABEL_SIZE]".
- ioctl(2) number changed from 50 to 53/54. I'll update the btrfs wiki page with regard to
  the number allocation to reflect this change if it is ok.


The old versions can be found at:

v3:
https://patchwork.kernel.org/patch/1124642/

v2:
http://permalink.gmane.org/gmane.comp.file-systems.btrfs/12877

v1:
http://permalink.gmane.org/gmane.comp.file-systems.btrfs/12872

Thanks,
-Jeff

[PATCH V4 1/2] Btrfs: Add a new ioctl to get the label of a mounted filesystem

[Jeff Liu]

Introduce a new ioctl BTRFS_IOC_GET_FSLABEL, which would be used to fetch the label
of a mounted filesystem.

Signed-off-by: Jie Liu <jeff.liu@oracle.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>

---
 fs/btrfs/ioctl.c |   14 ++++++++++++++
 fs/btrfs/ioctl.h |    2 ++
 2 files changed, 16 insertions(+)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 8fcf9a5..b0a5e17 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3699,6 +3699,18 @@ out:
 	return ret;
 }
 
+static int btrfs_ioctl_get_fslabel(struct btrfs_root *root, void __user *arg)
+{
+	const char *label = root->fs_info->super_copy->label;
+	int ret;
+
+	mutex_lock(&root->fs_info->volume_mutex);
+	ret = copy_to_user(arg, label, strlen(label));
+	mutex_unlock(&root->fs_info->volume_mutex);
+
+	return ret ? -EFAULT : 0;
+}
+
 long btrfs_ioctl(struct file *file, unsigned int
 		cmd, unsigned long arg)
 {
@@ -3797,6 +3809,8 @@ long btrfs_ioctl(struct file *file, unsigned int
 		return btrfs_ioctl_qgroup_create(root, argp);
 	case BTRFS_IOC_QGROUP_LIMIT:
 		return btrfs_ioctl_qgroup_limit(root, argp);
+	case BTRFS_IOC_GET_FSLABEL:
+		return btrfs_ioctl_get_fslabel(root, argp);
 	}
 
 	return -ENOTTY;
diff --git a/fs/btrfs/ioctl.h b/fs/btrfs/ioctl.h
index 731e287..98f896f 100644
--- a/fs/btrfs/ioctl.h
+++ b/fs/btrfs/ioctl.h
@@ -453,4 +453,6 @@ struct btrfs_ioctl_send_args {
 			       struct btrfs_ioctl_qgroup_limit_args)
 #define BTRFS_IOC_GET_DEV_STATS _IOWR(BTRFS_IOCTL_MAGIC, 52, \
 				      struct btrfs_ioctl_get_dev_stats)
+#define BTRFS_IOC_GET_FSLABEL _IOR(BTRFS_IOCTL_MAGIC, 53, \
+				   char[BTRFS_LABEL_SIZE])
 #endif
-- 
1.7.9.5

[PATCH V4 2/2] Btrfs: Add a new ioctl to change the label of a mounted filesystem

[Jeff Liu]

Add a new ioctl BTRFS_FS_SETLABEL to change the label of a mounted filesystem.

Signed-off-by: Jie Liu <jeff.liu@oracle.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>

---
 fs/btrfs/ioctl.c |   14 ++++++++++++++
 fs/btrfs/ioctl.h |    2 ++
 2 files changed, 16 insertions(+)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 8fcf9a5..b0a5e17 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3699,6 +3699,18 @@ out:
 	return ret;
 }
 
+static int btrfs_ioctl_get_fslabel(struct btrfs_root *root, void __user *arg)
+{
+	const char *label = root->fs_info->super_copy->label;
+	int ret;
+
+	mutex_lock(&root->fs_info->volume_mutex);
+	ret = copy_to_user(arg, label, strlen(label));
+	mutex_unlock(&root->fs_info->volume_mutex);
+
+	return ret ? -EFAULT : 0;
+}
+
 long btrfs_ioctl(struct file *file, unsigned int
 		cmd, unsigned long arg)
 {
@@ -3797,6 +3809,8 @@ long btrfs_ioctl(struct file *file, unsigned int
 		return btrfs_ioctl_qgroup_create(root, argp);
 	case BTRFS_IOC_QGROUP_LIMIT:
 		return btrfs_ioctl_qgroup_limit(root, argp);
+	case BTRFS_IOC_GET_FSLABEL:
+		return btrfs_ioctl_get_fslabel(root, argp);
 	}
 
 	return -ENOTTY;
diff --git a/fs/btrfs/ioctl.h b/fs/btrfs/ioctl.h
index 731e287..98f896f 100644
--- a/fs/btrfs/ioctl.h
+++ b/fs/btrfs/ioctl.h
@@ -453,4 +453,6 @@ struct btrfs_ioctl_send_args {
 			       struct btrfs_ioctl_qgroup_limit_args)
 #define BTRFS_IOC_GET_DEV_STATS _IOWR(BTRFS_IOCTL_MAGIC, 52, \
 				      struct btrfs_ioctl_get_dev_stats)
+#define BTRFS_IOC_GET_FSLABEL _IOR(BTRFS_IOCTL_MAGIC, 53, \
+				   char[BTRFS_LABEL_SIZE])
 #endif
-- 
1.7.9.5

jeff@koala:/usr/src/linux$ cat btrfs_label_v3/0002-set-label.patch 
Signed-off-by: Jie Liu <jeff.liu@oracle.com>

---
 fs/btrfs/ioctl.c |   34 ++++++++++++++++++++++++++++++++++
 fs/btrfs/ioctl.h |    2 ++
 2 files changed, 36 insertions(+)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index b0a5e17..ebbf634 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3711,6 +3711,38 @@ static int btrfs_ioctl_get_fslabel(struct btrfs_root *root, void __user *arg)
 	return ret ? -EFAULT : 0;
 }
 
+static int btrfs_ioctl_set_fslabel(struct btrfs_root *root, void __user *arg)
+{
+	struct btrfs_super_block *super_block = root->fs_info->super_copy;
+	struct btrfs_trans_handle *trans;
+	char label[BTRFS_LABEL_SIZE];
+	int ret = 0;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	if (btrfs_root_readonly(root))
+		return -EROFS;
+
+	if (copy_from_user(label, arg, sizeof(label)))
+		return -EFAULT;
+
+	label[BTRFS_LABEL_SIZE - 1] = '\0';
+
+	mutex_lock(&root->fs_info->volume_mutex);
+	trans = btrfs_start_transaction(root, 1);
+	if (IS_ERR(trans)) {
+		ret = PTR_ERR(trans);
+		goto out_unlock;
+	}
+	strcpy(super_block->label, label);
+	btrfs_end_transaction(trans, root);
+
+out_unlock:
+	mutex_unlock(&root->fs_info->volume_mutex);
+	return ret;
+}
+
 long btrfs_ioctl(struct file *file, unsigned int
 		cmd, unsigned long arg)
 {
@@ -3811,6 +3843,8 @@ long btrfs_ioctl(struct file *file, unsigned int
 		return btrfs_ioctl_qgroup_limit(root, argp);
 	case BTRFS_IOC_GET_FSLABEL:
 		return btrfs_ioctl_get_fslabel(root, argp);
+	case BTRFS_IOC_SET_FSLABEL:
+		return btrfs_ioctl_set_fslabel(root, argp);
 	}
 
 	return -ENOTTY;
diff --git a/fs/btrfs/ioctl.h b/fs/btrfs/ioctl.h
index 98f896f..cc4e657 100644
--- a/fs/btrfs/ioctl.h
+++ b/fs/btrfs/ioctl.h
@@ -455,4 +455,6 @@ struct btrfs_ioctl_send_args {
 				      struct btrfs_ioctl_get_dev_stats)
 #define BTRFS_IOC_GET_FSLABEL _IOR(BTRFS_IOCTL_MAGIC, 53, \
 				   char[BTRFS_LABEL_SIZE])
+#define BTRFS_IOC_SET_FSLABEL _IOW(BTRFS_IOCTL_MAGIC, 54, \
+				   char[BTRFS_LABEL_SIZE])
 #endif
-- 
1.7.9.5

[PATCH v4 1/3] Btrfs-progs: get the label of a mounted filesystem

[Jeff Liu]

Get the label of a mounted filesystem through the new ioctl BTRFS_IOCTL_FS_GETLABEL.

Signed-off-by: Jie Liu <jeff.liu@oracle.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>

---
 btrfslabel.c |   68 +++++++++++++++++++++++++++++++++++++---------------------
 ioctl.h      |    2 ++
 utils.c      |    2 +-
 utils.h      |    1 +
 4 files changed, 47 insertions(+), 26 deletions(-)

diff --git a/btrfslabel.c b/btrfslabel.c
index cb142b0..761a312 100644
--- a/btrfslabel.c
+++ b/btrfslabel.c
@@ -67,45 +67,63 @@ static void change_label_unmounted(char *dev, char *nLabel)
        close_ctree(root);
 }
 
-int get_label_unmounted(char *dev)
+static int get_label_unmounted(const char *dev)
 {
-       struct btrfs_root *root;
+	struct btrfs_root *root;
+	int ret;
 
-       /* Open the super_block at the default location
-        * and as read-only.
-        */
-       root = open_ctree(dev, 0, 0);
+	ret = check_mounted(dev);
+	if (ret < 0) {
+	       fprintf(stderr, "FATAL: error checking %s mount status\n", dev);
+	       return -1;
+	}
 
-       if(!root)
-         return -1;
+	/* Open the super_block at the default location
+	 * and as read-only.
+	 */
+	root = open_ctree(dev, 0, 0);
+	if(!root)
+		return -1;
 
-       fprintf(stdout, "%s\n", root->fs_info->super_copy.label);
+	fprintf(stdout, "%s\n", root->fs_info->super_copy.label);
 
-       /* Now we close it since we are done. */
-       close_ctree(root);
-       return 0;
+	/* Now we close it since we are done. */
+	close_ctree(root);
+	return 0;
 }
 
-int get_label(char *btrfs_dev)
+/*
+ * If a partition is mounted, try to get the filesystem label via its
+ * mounted path rather than device.  Return the corresponding error
+ * the user specified the device path.
+ */
+static int get_label_mounted(const char *mount_path)
 {
+	char label[BTRFS_LABEL_SIZE];
+	int fd;
 
-	int ret;
-	ret = check_mounted(btrfs_dev);
-	if (ret < 0)
-	{
-	       fprintf(stderr, "FATAL: error checking %s mount status\n", btrfs_dev);
-	       return -1;
+	fd = open(mount_path, O_RDONLY | O_NOATIME);
+	if (fd < 0) {
+		fprintf(stderr, "ERROR: unable access to '%s'\n", mount_path);
+		return -1;
 	}
 
-	if(ret != 0)
-	{
-	       fprintf(stderr, "FATAL: the filesystem has to be unmounted\n");
-	       return -2;
+	if (ioctl(fd, BTRFS_IOC_GET_FSLABEL, label) < 0) {
+		fprintf(stderr, "ERROR: unable get label %s\n", strerror(errno));
+		close(fd);
+		return -1;
 	}
-	ret = get_label_unmounted(btrfs_dev);
-	return ret;
+
+	fprintf(stdout, "%s\n", label);
+	return 0;
 }
 
+int get_label(const char *btrfs_dev)
+{
+	return is_existing_blk_or_reg_file(btrfs_dev) ?
+		get_label_unmounted(btrfs_dev) :
+		get_label_mounted(btrfs_dev);
+}
 
 int set_label(char *btrfs_dev, char *nLabel)
 {
diff --git a/ioctl.h b/ioctl.h
index 6fda3a1..ed6784d 100644
--- a/ioctl.h
+++ b/ioctl.h
@@ -432,4 +432,6 @@ struct btrfs_ioctl_clone_range_args {
 					struct btrfs_ioctl_qgroup_create_args)
 #define BTRFS_IOC_QGROUP_LIMIT _IOR(BTRFS_IOCTL_MAGIC, 43, \
 					struct btrfs_ioctl_qgroup_limit_args)
+#define BTRFS_IOC_GET_FSLABEL _IOR(BTRFS_IOCTL_MAGIC, 53, \
+				   char[BTRFS_LABEL_SIZE])
 #endif
diff --git a/utils.c b/utils.c
index 205e667..d59bca3 100644
--- a/utils.c
+++ b/utils.c
@@ -811,7 +811,7 @@ int check_mounted(const char* file)
 		return -errno;
 	}
 
-	ret =  check_mounted_where(fd, file, NULL, 0, NULL);
+	ret = check_mounted_where(fd, file, NULL, 0, NULL);
 	close(fd);
 
 	return ret;
diff --git a/utils.h b/utils.h
index 3a0368b..8750f28 100644
--- a/utils.h
+++ b/utils.h
@@ -46,4 +46,5 @@ int check_label(char *input);
 int get_mountpt(char *dev, char *mntpt, size_t size);
 
 int btrfs_scan_block_devices(int run_ioctl);
+int is_existing_blk_or_reg_file(const char* filename);
 #endif
-- 
1.7.9.5

[PATCH v4 2/3] Btrfs-progs: change the label of a mounted filesystem

[Jeff Liu]

Change the label of a mounted file system through the new ioctl BTRFS_IOCTL_FS_SETLABEL.

Signed-off-by: Jie Liu <jeff.liu@oracle.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>

---
 btrfslabel.c |   84 ++++++++++++++++++++++++++++++++++------------------------
 ioctl.h      |    2 ++
 2 files changed, 51 insertions(+), 35 deletions(-)

diff --git a/btrfslabel.c b/btrfslabel.c
index 761a312..65388e5 100644
--- a/btrfslabel.c
+++ b/btrfslabel.c
@@ -46,25 +46,52 @@
 #define GET_LABEL                      3
 #define SET_LABEL                      4
 
-static void change_label_unmounted(char *dev, char *nLabel)
+static int set_label_unmounted(const char *dev, const char *label)
 {
-       struct btrfs_root *root;
-       struct btrfs_trans_handle *trans;
-
-       /* Open the super_block at the default location
-        * and as read-write.
-        */
-       root = open_ctree(dev, 0, 1);
-       if (!root) /* errors are printed by open_ctree() */
-         return;
-
-       trans = btrfs_start_transaction(root, 1);
-       strncpy(root->fs_info->super_copy.label, nLabel, BTRFS_LABEL_SIZE);
-       root->fs_info->super_copy.label[BTRFS_LABEL_SIZE-1] = 0;
-       btrfs_commit_transaction(trans, root);
-
-       /* Now we close it since we are done. */
-       close_ctree(root);
+	struct btrfs_trans_handle *trans;
+	struct btrfs_root *root;
+	int ret;
+
+	ret = check_mounted(dev);
+	if (ret < 0) {
+	       fprintf(stderr, "FATAL: error checking %s mount status\n", dev);
+	       return -1;
+	}
+
+	/* Open the super_block at the default location
+	 * and as read-write.
+	 */
+	root = open_ctree(dev, 0, 1);
+	if (!root) /* errors are printed by open_ctree() */
+		return -1;
+
+	trans = btrfs_start_transaction(root, 1);
+	strncpy(root->fs_info->super_copy.label, label, BTRFS_LABEL_SIZE);
+	root->fs_info->super_copy.label[BTRFS_LABEL_SIZE-1] = 0;
+	btrfs_commit_transaction(trans, root);
+
+	/* Now we close it since we are done. */
+	close_ctree(root);
+	return 0;
+}
+
+static int set_label_mounted(const char *mount_path, const char *label)
+{
+	int fd;
+
+	fd = open(mount_path, O_RDONLY | O_NOATIME);
+	if (fd < 0) {
+		fprintf(stderr, "ERROR: unable access to '%s'\n", mount_path);
+		return -1;
+	}
+
+	if (ioctl(fd, BTRFS_IOC_SET_FSLABEL, label) < 0) {
+		fprintf(stderr, "ERROR: unable get label %s\n", strerror(errno));
+		close(fd);
+		return -1;
+	}
+
+	return 0;
 }
 
 static int get_label_unmounted(const char *dev)
@@ -125,22 +152,9 @@ int get_label(const char *btrfs_dev)
 		get_label_mounted(btrfs_dev);
 }
 
-int set_label(char *btrfs_dev, char *nLabel)
+int set_label(char *btrfs_dev, char *label)
 {
-
-	int ret;
-	ret = check_mounted(btrfs_dev);
-	if (ret < 0)
-	{
-	       fprintf(stderr, "FATAL: error checking %s mount status\n", btrfs_dev);
-	       return -1;
-	}
-
-	if(ret != 0)
-	{
-	       fprintf(stderr, "FATAL: the filesystem has to be unmounted\n");
-	       return -2;
-	}
-	change_label_unmounted(btrfs_dev, nLabel);
-	return 0;
+	return is_existing_blk_or_reg_file(btrfs_dev) ?
+		set_label_unmounted(btrfs_dev, label) :
+		set_label_mounted(btrfs_dev, label);
 }
diff --git a/ioctl.h b/ioctl.h
index ed6784d..07259f9 100644
--- a/ioctl.h
+++ b/ioctl.h
@@ -434,4 +434,6 @@ struct btrfs_ioctl_clone_range_args {
 					struct btrfs_ioctl_qgroup_limit_args)
 #define BTRFS_IOC_GET_FSLABEL _IOR(BTRFS_IOCTL_MAGIC, 53, \
 				   char[BTRFS_LABEL_SIZE])
+#define BTRFS_IOC_SET_FSLABEL _IOW(BTRFS_IOCTL_MAGIC, 54, \
+				   char[BTRFS_LABEL_SIZE])
 #endif
-- 
1.7.9.5

[PATCH v4 3/3] Btrfs-progs: fix cmd_label_usage to reflect this change.

[Jeff Liu]

Fix the command usage of "btrfs filesystem label" to reflect this change. i.e. so that
we can get/set the label of a mounted filesystem against the mountpoint.

Signed-off-by: Jie Liu <jeff.liu@oracle.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>

---
 cmds-filesystem.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/cmds-filesystem.c b/cmds-filesystem.c
index 9c43d35..5770d8b 100644
--- a/cmds-filesystem.c
+++ b/cmds-filesystem.c
@@ -517,8 +517,8 @@ static int cmd_resize(int argc, char **argv)
 }
 
 static const char * const cmd_label_usage[] = {
-	"btrfs filesystem label <device> [<newlabel>]",
-	"Get or change the label of an unmounted filesystem",
+	"btrfs filesystem label [<device>|<mountpoint>] [<newlabel>]",
+	"Get or change the label of a filesystem",
 	"With one argument, get the label of filesystem on <device>.",
 	"If <newlabel> is passed, set the filesystem label to <newlabel>.",
 	NULL
-- 
1.7.9.5

Re: [PATCH V4 2/2] Btrfs: Add a new ioctl to change the label of a mounted filesystem

[Miao Xie]

Hi, Liu

On wed, 12 Dec 2012 08:22:28 +0800, Jeff Liu wrote:
> Add a new ioctl BTRFS_FS_SETLABEL to change the label of a mounted filesystem.
> 
> Signed-off-by: Jie Liu <jeff.liu@oracle.com>
> Signed-off-by: Anand Jain <anand.jain@oracle.com>
> 
> ---
>  fs/btrfs/ioctl.c |   14 ++++++++++++++
>  fs/btrfs/ioctl.h |    2 ++
>  2 files changed, 16 insertions(+)
> 
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index 8fcf9a5..b0a5e17 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -3699,6 +3699,18 @@ out:
>  	return ret;
>  }
>  
> +static int btrfs_ioctl_get_fslabel(struct btrfs_root *root, void __user *arg)
> +{
> +	const char *label = root->fs_info->super_copy->label;
> +	int ret;
> +
> +	mutex_lock(&root->fs_info->volume_mutex);
> +	ret = copy_to_user(arg, label, strlen(label));
> +	mutex_unlock(&root->fs_info->volume_mutex);
> +
> +	return ret ? -EFAULT : 0;
> +}


You sent out a wrong patch.

Thanks
Miao

> +
>  long btrfs_ioctl(struct file *file, unsigned int
>  		cmd, unsigned long arg)
>  {
> @@ -3797,6 +3809,8 @@ long btrfs_ioctl(struct file *file, unsigned int
>  		return btrfs_ioctl_qgroup_create(root, argp);
>  	case BTRFS_IOC_QGROUP_LIMIT:
>  		return btrfs_ioctl_qgroup_limit(root, argp);
> +	case BTRFS_IOC_GET_FSLABEL:
> +		return btrfs_ioctl_get_fslabel(root, argp);
>  	}
>  
>  	return -ENOTTY;
> diff --git a/fs/btrfs/ioctl.h b/fs/btrfs/ioctl.h
> index 731e287..98f896f 100644
> --- a/fs/btrfs/ioctl.h
> +++ b/fs/btrfs/ioctl.h
> @@ -453,4 +453,6 @@ struct btrfs_ioctl_send_args {
>  			       struct btrfs_ioctl_qgroup_limit_args)
>  #define BTRFS_IOC_GET_DEV_STATS _IOWR(BTRFS_IOCTL_MAGIC, 52, \
>  				      struct btrfs_ioctl_get_dev_stats)
> +#define BTRFS_IOC_GET_FSLABEL _IOR(BTRFS_IOCTL_MAGIC, 53, \
> +				   char[BTRFS_LABEL_SIZE])
>  #endif
> 

Re: [PATCH V4 2/2] Btrfs: Add a new ioctl to change the label of a mounted filesystem

[Jeff Liu]

Hi Miao,

On 12/12/2012 11:03 AM, Miao Xie wrote:
> Hi, Liu
> 
> On wed, 12 Dec 2012 08:22:28 +0800, Jeff Liu wrote:
>> Add a new ioctl BTRFS_FS_SETLABEL to change the label of a mounted filesystem.
>>
>> Signed-off-by: Jie Liu <jeff.liu@oracle.com>
>> Signed-off-by: Anand Jain <anand.jain@oracle.com>
>>
>> ---
>>  fs/btrfs/ioctl.c |   14 ++++++++++++++
>>  fs/btrfs/ioctl.h |    2 ++
>>  2 files changed, 16 insertions(+)
>>
>> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
>> index 8fcf9a5..b0a5e17 100644
>> --- a/fs/btrfs/ioctl.c
>> +++ b/fs/btrfs/ioctl.c
>> @@ -3699,6 +3699,18 @@ out:
>>  	return ret;
>>  }
>>  
>> +static int btrfs_ioctl_get_fslabel(struct btrfs_root *root, void __user *arg)
>> +{
>> +	const char *label = root->fs_info->super_copy->label;
>> +	int ret;
>> +
>> +	mutex_lock(&root->fs_info->volume_mutex);
>> +	ret = copy_to_user(arg, label, strlen(label));
>> +	mutex_unlock(&root->fs_info->volume_mutex);
>> +
>> +	return ret ? -EFAULT : 0;
>> +}
> 
> 
> You sent out a wrong patch.
Ah! I should not send patches out during my sleepy state, will re-send
them a little while, thank you. :)

-Jeff
> 
> Thanks
> Miao
> 
>> +
>>  long btrfs_ioctl(struct file *file, unsigned int
>>  		cmd, unsigned long arg)
>>  {
>> @@ -3797,6 +3809,8 @@ long btrfs_ioctl(struct file *file, unsigned int
>>  		return btrfs_ioctl_qgroup_create(root, argp);
>>  	case BTRFS_IOC_QGROUP_LIMIT:
>>  		return btrfs_ioctl_qgroup_limit(root, argp);
>> +	case BTRFS_IOC_GET_FSLABEL:
>> +		return btrfs_ioctl_get_fslabel(root, argp);
>>  	}
>>  
>>  	return -ENOTTY;
>> diff --git a/fs/btrfs/ioctl.h b/fs/btrfs/ioctl.h
>> index 731e287..98f896f 100644
>> --- a/fs/btrfs/ioctl.h
>> +++ b/fs/btrfs/ioctl.h
>> @@ -453,4 +453,6 @@ struct btrfs_ioctl_send_args {
>>  			       struct btrfs_ioctl_qgroup_limit_args)
>>  #define BTRFS_IOC_GET_DEV_STATS _IOWR(BTRFS_IOCTL_MAGIC, 52, \
>>  				      struct btrfs_ioctl_get_dev_stats)
>> +#define BTRFS_IOC_GET_FSLABEL _IOR(BTRFS_IOCTL_MAGIC, 53, \
>> +				   char[BTRFS_LABEL_SIZE])
>>  #endif
>>
> 

[RESEND PATCH V4 1/2] Btrfs: Add a new ioctl to get the label of a mounted filesystem

[Jeff Liu]

Signed-off-by: Jie Liu <jeff.liu@oracle.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>

---
 fs/btrfs/ioctl.c |   14 ++++++++++++++
 fs/btrfs/ioctl.h |    2 ++
 2 files changed, 16 insertions(+)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 8fcf9a5..b0a5e17 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3699,6 +3699,18 @@ out:
 	return ret;
 }
 
+static int btrfs_ioctl_get_fslabel(struct btrfs_root *root, void __user *arg)
+{
+	const char *label = root->fs_info->super_copy->label;
+	int ret;
+
+	mutex_lock(&root->fs_info->volume_mutex);
+	ret = copy_to_user(arg, label, strlen(label));
+	mutex_unlock(&root->fs_info->volume_mutex);
+
+	return ret ? -EFAULT : 0;
+}
+
 long btrfs_ioctl(struct file *file, unsigned int
 		cmd, unsigned long arg)
 {
@@ -3797,6 +3809,8 @@ long btrfs_ioctl(struct file *file, unsigned int
 		return btrfs_ioctl_qgroup_create(root, argp);
 	case BTRFS_IOC_QGROUP_LIMIT:
 		return btrfs_ioctl_qgroup_limit(root, argp);
+	case BTRFS_IOC_GET_FSLABEL:
+		return btrfs_ioctl_get_fslabel(root, argp);
 	}
 
 	return -ENOTTY;
diff --git a/fs/btrfs/ioctl.h b/fs/btrfs/ioctl.h
index 731e287..98f896f 100644
--- a/fs/btrfs/ioctl.h
+++ b/fs/btrfs/ioctl.h
@@ -453,4 +453,6 @@ struct btrfs_ioctl_send_args {
 			       struct btrfs_ioctl_qgroup_limit_args)
 #define BTRFS_IOC_GET_DEV_STATS _IOWR(BTRFS_IOCTL_MAGIC, 52, \
 				      struct btrfs_ioctl_get_dev_stats)
+#define BTRFS_IOC_GET_FSLABEL _IOR(BTRFS_IOCTL_MAGIC, 53, \
+				   char[BTRFS_LABEL_SIZE])
 #endif
-- 
1.7.9.5

[RESEND PATCH V4 2/2] Btrfs: Add a new ioctl to change the label of a mounted filesystem

[Jeff Liu]

Add a new ioctl BTRFS_FS_SETLABEL to change the label of a mounted filesystem.


Signed-off-by: Jie Liu <jeff.liu@oracle.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>

---
 fs/btrfs/ioctl.c |   34 ++++++++++++++++++++++++++++++++++
 fs/btrfs/ioctl.h |    2 ++
 2 files changed, 36 insertions(+)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index b0a5e17..ebbf634 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -3711,6 +3711,38 @@ static int btrfs_ioctl_get_fslabel(struct btrfs_root *root, void __user *arg)
 	return ret ? -EFAULT : 0;
 }
 
+static int btrfs_ioctl_set_fslabel(struct btrfs_root *root, void __user *arg)
+{
+	struct btrfs_super_block *super_block = root->fs_info->super_copy;
+	struct btrfs_trans_handle *trans;
+	char label[BTRFS_LABEL_SIZE];
+	int ret = 0;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	if (btrfs_root_readonly(root))
+		return -EROFS;
+
+	if (copy_from_user(label, arg, sizeof(label)))
+		return -EFAULT;
+
+	label[BTRFS_LABEL_SIZE - 1] = '\0';
+
+	mutex_lock(&root->fs_info->volume_mutex);
+	trans = btrfs_start_transaction(root, 1);
+	if (IS_ERR(trans)) {
+		ret = PTR_ERR(trans);
+		goto out_unlock;
+	}
+	strcpy(super_block->label, label);
+	btrfs_end_transaction(trans, root);
+
+out_unlock:
+	mutex_unlock(&root->fs_info->volume_mutex);
+	return ret;
+}
+
 long btrfs_ioctl(struct file *file, unsigned int
 		cmd, unsigned long arg)
 {
@@ -3811,6 +3843,8 @@ long btrfs_ioctl(struct file *file, unsigned int
 		return btrfs_ioctl_qgroup_limit(root, argp);
 	case BTRFS_IOC_GET_FSLABEL:
 		return btrfs_ioctl_get_fslabel(root, argp);
+	case BTRFS_IOC_SET_FSLABEL:
+		return btrfs_ioctl_set_fslabel(root, argp);
 	}
 
 	return -ENOTTY;
diff --git a/fs/btrfs/ioctl.h b/fs/btrfs/ioctl.h
index 98f896f..cc4e657 100644
--- a/fs/btrfs/ioctl.h
+++ b/fs/btrfs/ioctl.h
@@ -455,4 +455,6 @@ struct btrfs_ioctl_send_args {
 				      struct btrfs_ioctl_get_dev_stats)
 #define BTRFS_IOC_GET_FSLABEL _IOR(BTRFS_IOCTL_MAGIC, 53, \
 				   char[BTRFS_LABEL_SIZE])
+#define BTRFS_IOC_SET_FSLABEL _IOW(BTRFS_IOCTL_MAGIC, 54, \
+				   char[BTRFS_LABEL_SIZE])
 #endif
-- 
1.7.9.5

Re: [RESEND PATCH V4 1/2] Btrfs: Add a new ioctl to get the label of a mounted filesystem

[Miao Xie]

On Wed, 12 Dec 2012 11:22:49 +0800, Jeff Liu wrote:
> Signed-off-by: Jie Liu <jeff.liu@oracle.com>
> Signed-off-by: Anand Jain <anand.jain@oracle.com>
> 
> ---
>  fs/btrfs/ioctl.c |   14 ++++++++++++++
>  fs/btrfs/ioctl.h |    2 ++
>  2 files changed, 16 insertions(+)
> 
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index 8fcf9a5..b0a5e17 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -3699,6 +3699,18 @@ out:
>  	return ret;
>  }
>  
> +static int btrfs_ioctl_get_fslabel(struct btrfs_root *root, void __user *arg)
> +{
> +	const char *label = root->fs_info->super_copy->label;
> +	int ret;
> +
> +	mutex_lock(&root->fs_info->volume_mutex);
> +	ret = copy_to_user(arg, label, strlen(label));
> +	mutex_unlock(&root->fs_info->volume_mutex);
> +
> +	return ret ? -EFAULT : 0;
> +}
> +
>  long btrfs_ioctl(struct file *file, unsigned int
>  		cmd, unsigned long arg)
>  {
> @@ -3797,6 +3809,8 @@ long btrfs_ioctl(struct file *file, unsigned int
>  		return btrfs_ioctl_qgroup_create(root, argp);
>  	case BTRFS_IOC_QGROUP_LIMIT:
>  		return btrfs_ioctl_qgroup_limit(root, argp);
> +	case BTRFS_IOC_GET_FSLABEL:
> +		return btrfs_ioctl_get_fslabel(root, argp);
>  	}
>  
>  	return -ENOTTY;
> diff --git a/fs/btrfs/ioctl.h b/fs/btrfs/ioctl.h
> index 731e287..98f896f 100644
> --- a/fs/btrfs/ioctl.h
> +++ b/fs/btrfs/ioctl.h
> @@ -453,4 +453,6 @@ struct btrfs_ioctl_send_args {
>  			       struct btrfs_ioctl_qgroup_limit_args)
>  #define BTRFS_IOC_GET_DEV_STATS _IOWR(BTRFS_IOCTL_MAGIC, 52, \
>  				      struct btrfs_ioctl_get_dev_stats)
> +#define BTRFS_IOC_GET_FSLABEL _IOR(BTRFS_IOCTL_MAGIC, 53, \
> +				   char[BTRFS_LABEL_SIZE])
>  #endif
> 

According to the project idea web,
	https://btrfs.wiki.kernel.org/index.php/Project_ideas#Development_notes.2C_please_read

number 53 has been used for the drive swapping commands, so I think we should
choose another one. Maybe 49 is good since the above web says number 50 has been
reserved for set/change label command.

Re: [RESEND PATCH V4 1/2] Btrfs: Add a new ioctl to get the label of a mounted filesystem

[Jeff Liu]

On 12/12/2012 11:50 AM, Miao Xie wrote:
> On Wed, 12 Dec 2012 11:22:49 +0800, Jeff Liu wrote:
>> Signed-off-by: Jie Liu <jeff.liu@oracle.com>
>> Signed-off-by: Anand Jain <anand.jain@oracle.com>
>>
>> ---
>>  fs/btrfs/ioctl.c |   14 ++++++++++++++
>>  fs/btrfs/ioctl.h |    2 ++
>>  2 files changed, 16 insertions(+)
>>
>> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
>> index 8fcf9a5..b0a5e17 100644
>> --- a/fs/btrfs/ioctl.c
>> +++ b/fs/btrfs/ioctl.c
>> @@ -3699,6 +3699,18 @@ out:
>>  	return ret;
>>  }
>>  
>> +static int btrfs_ioctl_get_fslabel(struct btrfs_root *root, void __user *arg)
>> +{
>> +	const char *label = root->fs_info->super_copy->label;
>> +	int ret;
>> +
>> +	mutex_lock(&root->fs_info->volume_mutex);
>> +	ret = copy_to_user(arg, label, strlen(label));
>> +	mutex_unlock(&root->fs_info->volume_mutex);
>> +
>> +	return ret ? -EFAULT : 0;
>> +}
>> +
>>  long btrfs_ioctl(struct file *file, unsigned int
>>  		cmd, unsigned long arg)
>>  {
>> @@ -3797,6 +3809,8 @@ long btrfs_ioctl(struct file *file, unsigned int
>>  		return btrfs_ioctl_qgroup_create(root, argp);
>>  	case BTRFS_IOC_QGROUP_LIMIT:
>>  		return btrfs_ioctl_qgroup_limit(root, argp);
>> +	case BTRFS_IOC_GET_FSLABEL:
>> +		return btrfs_ioctl_get_fslabel(root, argp);
>>  	}
>>  
>>  	return -ENOTTY;
>> diff --git a/fs/btrfs/ioctl.h b/fs/btrfs/ioctl.h
>> index 731e287..98f896f 100644
>> --- a/fs/btrfs/ioctl.h
>> +++ b/fs/btrfs/ioctl.h
>> @@ -453,4 +453,6 @@ struct btrfs_ioctl_send_args {
>>  			       struct btrfs_ioctl_qgroup_limit_args)
>>  #define BTRFS_IOC_GET_DEV_STATS _IOWR(BTRFS_IOCTL_MAGIC, 52, \
>>  				      struct btrfs_ioctl_get_dev_stats)
>> +#define BTRFS_IOC_GET_FSLABEL _IOR(BTRFS_IOCTL_MAGIC, 53, \
>> +				   char[BTRFS_LABEL_SIZE])
>>  #endif
>>
> 
> According to the project idea web,
> 	https://btrfs.wiki.kernel.org/index.php/Project_ideas#Development_notes.2C_please_read
> 
> number 53 has been used for the drive swapping commands, so I think we should
> choose another one. Maybe 49 is good since the above web says number 50 has been
> reserved for set/change label command.
Ok, let's waiting for others comments, I'll follow up the final
confirmation.

Thanks,
-Jeff
> --
> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 

Re: [RESEND PATCH V4 2/2] Btrfs: Add a new ioctl to change the label of a mounted filesystem

[Miao Xie]

On wed, 12 Dec 2012 11:23:00 +0800, Jeff Liu wrote:
> Add a new ioctl BTRFS_FS_SETLABEL to change the label of a mounted filesystem.
> 
> 
> Signed-off-by: Jie Liu <jeff.liu@oracle.com>
> Signed-off-by: Anand Jain <anand.jain@oracle.com>
> 
> ---
>  fs/btrfs/ioctl.c |   34 ++++++++++++++++++++++++++++++++++
>  fs/btrfs/ioctl.h |    2 ++
>  2 files changed, 36 insertions(+)
> 
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index b0a5e17..ebbf634 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -3711,6 +3711,38 @@ static int btrfs_ioctl_get_fslabel(struct btrfs_root *root, void __user *arg)
>  	return ret ? -EFAULT : 0;
>  }
>  
> +static int btrfs_ioctl_set_fslabel(struct btrfs_root *root, void __user *arg)
> +{
> +	struct btrfs_super_block *super_block = root->fs_info->super_copy;
> +	struct btrfs_trans_handle *trans;
> +	char label[BTRFS_LABEL_SIZE];
> +	int ret = 0;
> +
> +	if (!capable(CAP_SYS_ADMIN))
> +		return -EPERM;
> +
> +	if (btrfs_root_readonly(root))
> +		return -EROFS;

Since this label is a global parameter, we needn't check the root
is R/O or not.

The check we need is the write access of the fs, so we need call
	mnt_want_write_file()

> +
> +	if (copy_from_user(label, arg, sizeof(label)))
> +		return -EFAULT;
> +
> +	label[BTRFS_LABEL_SIZE - 1] = '\0';

I don't think setting the last byte to '\0' is a good way, because the user would be
very strange that the new label is truncated, but the program told him that it was done
successfully.

> +
> +	mutex_lock(&root->fs_info->volume_mutex);
> +	trans = btrfs_start_transaction(root, 1);
> +	if (IS_ERR(trans)) {
> +		ret = PTR_ERR(trans);
> +		goto out_unlock;
> +	}
> +	strcpy(super_block->label, label);
> +	btrfs_end_transaction(trans, root);
> +
> +out_unlock:
> +	mutex_unlock(&root->fs_info->volume_mutex);
> +	return ret;
> +}
> +
>  long btrfs_ioctl(struct file *file, unsigned int
>  		cmd, unsigned long arg)
>  {
> @@ -3811,6 +3843,8 @@ long btrfs_ioctl(struct file *file, unsigned int
>  		return btrfs_ioctl_qgroup_limit(root, argp);
>  	case BTRFS_IOC_GET_FSLABEL:
>  		return btrfs_ioctl_get_fslabel(root, argp);
> +	case BTRFS_IOC_SET_FSLABEL:
> +		return btrfs_ioctl_set_fslabel(root, argp);
>  	}
>  
>  	return -ENOTTY;
> diff --git a/fs/btrfs/ioctl.h b/fs/btrfs/ioctl.h
> index 98f896f..cc4e657 100644
> --- a/fs/btrfs/ioctl.h
> +++ b/fs/btrfs/ioctl.h
> @@ -455,4 +455,6 @@ struct btrfs_ioctl_send_args {
>  				      struct btrfs_ioctl_get_dev_stats)
>  #define BTRFS_IOC_GET_FSLABEL _IOR(BTRFS_IOCTL_MAGIC, 53, \
>  				   char[BTRFS_LABEL_SIZE])
> +#define BTRFS_IOC_SET_FSLABEL _IOW(BTRFS_IOCTL_MAGIC, 54, \
> +				   char[BTRFS_LABEL_SIZE])
>  #endif

number 50 has been reserved for this feature.

Thanks
Miao

Re: [RESEND PATCH V4 2/2] Btrfs: Add a new ioctl to change the label of a mounted filesystem

[Jeff Liu]

Sorry for my late response, I missed your feedback somehow.
On 12/12/2012 12:15 PM, Miao Xie wrote:
> On wed, 12 Dec 2012 11:23:00 +0800, Jeff Liu wrote:
>> Add a new ioctl BTRFS_FS_SETLABEL to change the label of a mounted filesystem.
>>
>>
>> Signed-off-by: Jie Liu <jeff.liu@oracle.com>
>> Signed-off-by: Anand Jain <anand.jain@oracle.com>
>>
>> ---
>>  fs/btrfs/ioctl.c |   34 ++++++++++++++++++++++++++++++++++
>>  fs/btrfs/ioctl.h |    2 ++
>>  2 files changed, 36 insertions(+)
>>
>> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
>> index b0a5e17..ebbf634 100644
>> --- a/fs/btrfs/ioctl.c
>> +++ b/fs/btrfs/ioctl.c
>> @@ -3711,6 +3711,38 @@ static int btrfs_ioctl_get_fslabel(struct btrfs_root *root, void __user *arg)
>>  	return ret ? -EFAULT : 0;
>>  }
>>  
>> +static int btrfs_ioctl_set_fslabel(struct btrfs_root *root, void __user *arg)
>> +{
>> +	struct btrfs_super_block *super_block = root->fs_info->super_copy;
>> +	struct btrfs_trans_handle *trans;
>> +	char label[BTRFS_LABEL_SIZE];
>> +	int ret = 0;
>> +
>> +	if (!capable(CAP_SYS_ADMIN))
>> +		return -EPERM;
>> +
>> +	if (btrfs_root_readonly(root))
>> +		return -EROFS;
> 
> Since this label is a global parameter, we needn't check the root
> is R/O or not.
> 
> The check we need is the write access of the fs, so we need call
> 	mnt_want_write_file()
Yes, you are right.
> 
>> +
>> +	if (copy_from_user(label, arg, sizeof(label)))
>> +		return -EFAULT;
>> +
>> +	label[BTRFS_LABEL_SIZE - 1] = '\0';
> 
> I don't think setting the last byte to '\0' is a good way, because the user would be
> very strange that the new label is truncated, but the program told him that it was done
> successfully.
Good point, will revise it later.

Thanks,
-Jeff
> 
>> +
>> +	mutex_lock(&root->fs_info->volume_mutex);
>> +	trans = btrfs_start_transaction(root, 1);
>> +	if (IS_ERR(trans)) {
>> +		ret = PTR_ERR(trans);
>> +		goto out_unlock;
>> +	}
>> +	strcpy(super_block->label, label);
>> +	btrfs_end_transaction(trans, root);
>> +
>> +out_unlock:
>> +	mutex_unlock(&root->fs_info->volume_mutex);
>> +	return ret;
>> +}
>> +
>>  long btrfs_ioctl(struct file *file, unsigned int
>>  		cmd, unsigned long arg)
>>  {
>> @@ -3811,6 +3843,8 @@ long btrfs_ioctl(struct file *file, unsigned int
>>  		return btrfs_ioctl_qgroup_limit(root, argp);
>>  	case BTRFS_IOC_GET_FSLABEL:
>>  		return btrfs_ioctl_get_fslabel(root, argp);
>> +	case BTRFS_IOC_SET_FSLABEL:
>> +		return btrfs_ioctl_set_fslabel(root, argp);
>>  	}
>>  
>>  	return -ENOTTY;
>> diff --git a/fs/btrfs/ioctl.h b/fs/btrfs/ioctl.h
>> index 98f896f..cc4e657 100644
>> --- a/fs/btrfs/ioctl.h
>> +++ b/fs/btrfs/ioctl.h
>> @@ -455,4 +455,6 @@ struct btrfs_ioctl_send_args {
>>  				      struct btrfs_ioctl_get_dev_stats)
>>  #define BTRFS_IOC_GET_FSLABEL _IOR(BTRFS_IOCTL_MAGIC, 53, \
>>  				   char[BTRFS_LABEL_SIZE])
>> +#define BTRFS_IOC_SET_FSLABEL _IOW(BTRFS_IOCTL_MAGIC, 54, \
>> +				   char[BTRFS_LABEL_SIZE])
>>  #endif
> 
> number 50 has been reserved for this feature.
> 
> Thanks
> Miao
>